how do Pneumatic diaphragm pumps not feed

Pneumatic diaphragm pump can not feed a variety of reasons:
1. The pipe is sealed intact, if the leak will affect the self-absorption leads to feed exception.
2. The diaphragm is damaged, the valve seal valve seat is intact, otherwise it will lead to feed exception.
3. The valve action is normal, the pump is able to operate normally. If you have questions do valve component maintenance.
4.The material status, if the viscosity is too high, exceeding the selected application viscosity range of diaphragm pumps.
5. whether the self-absorption is feed, if suction is too long, resulting in not properly feed.